1. Field of the Invention
The present invention generally relates to semiconductor substrate processing systems. More specifically, the present invention relates to an apparatus for performing an etch process in a semiconductor substrate processing system.
2. Description of the Related Art
Reactive ion etch (RIE) is an important process in fabrication of integrated circuit (IC) devices. The RIE process is a plasma etch process that is performed in a chamber where a semiconductor substrate (e.g., a silicon (Si) wafer) is disposed on a substrate pedestal that is coupled to a source of radio-frequency (RF) power. Such chamber is generally referred to as a RIE chamber.
In the RIE chamber, application of the RF power to the substrate pedestal results in energizing an etchant gas to form a plasma that etches a material layer on a surface of the wafer, e.g., a low-K dielectric material such as an organic doped silicon glass (OSG). One major problem associated with the RIE process is that distribution of the plasma in the conventional RIE chamber is non-uniform due to a wafer edge effect and, as such, the etch rate across the wafer is non-uniform. More specifically, the etch rate at locations near an edge of the wafer is higher than the etch rate for points near a center of the wafer.
During fabrication of advanced IC devices using a dual damascene technique, the etch rate non-uniformity generally should be less than 5%. Herein the etch rate non-uniformity is defined as expressed in percent units ratio of a difference between the maximal and minimal etch rate within the substrate to a sum of such maximal and minimal etch rates.
Many attempts have been conducted to reduce the etch rate non-uniformity during the RIE process, including modifying an etchant gas distribution pattern in the chamber, substrate pedestal design, and the like. Other attempts to improve the etch rate non-uniformity have been focused on magnetizing a plasma in the RIE chamber, e.g., using solenoids or permanent magnets disposed around or above the chamber. Such RIE chamber with a magnetized plasma is known in the art as a magnetically enhanced reactive ion etch (MERIE) chamber.
While various methods of the prior art have demonstrated that the etch rate non-uniformity can be improved, specifically using the MERIE chamber, the etch rate non-uniformity remains about 10% for most applications related to etching the dielectric materials.
Therefore, there is a need in the art for an apparatus for etching, with low non-uniformity, a layer of a dielectric material during fabrication of an IC device.